1. Field of the Invention
The present invention relates to a method for diagnosing glioma by comparing the protein locations in an individual to be diagnosed with those of the normal control nerve cells. More particularly, the present invention relates to a method for diagnosing glioma comprising determining that an individual has glioma or of predicting prognosis after surgery of glioma when the expression level of GFRα4 in the endoplasmic reticulum is higher than that in the plasma membrane, and a method for screening a therapeutic agent for glioma. Further, the present invention relates to a method for diagnosing glioma or for predicting prognosis after surgery of glioma based on the number of GFRα4 and PSPN interactions.
2. Description of the Related Art
A change in the subcellular location of a protein is fundamental to cell function and regulatory control. Generally, protein location can be governed by signal peptides, which convey proteins to the specific organelle. It is also an important regulatory mechanism, as signal peptides can be modified by carrier proteins that recognize a particular pattern of modifications after translation of mRNA into peptide. For example, STAT3 (signal transducer and activator of transcription 3) is phosphorylated by various cytokines and growth signals, resulting in its relocation to the nucleus, where it serves as a strong DNA-binding transcriptional activator. Inappropriate phosphorylation and relocation of STAT3 are known to promote oncogenesis through abnormal cell cycle progression, angiogenesis, and invasion of tissue. Changes in protein location are also associated with genetic disorders. For instance, in Zellweger syndrome, relocation of peroxisomal proteins leads to dysfunctional fatty acid oxidation.
Therefore, functional changes of cells can be predicted through accurate identification of changes in the subcellular locations of proteins and the type of neighboring proteins.
Meanwhile, there are two types of brain tumors; primary brain tumors that originate in the brain itself and metastatic brain tumors that spread from other organs. Primary brain tumors can be further divided into two types of tumors—benign and malignant. Even if primary brain tumors are benign, benign tumors can compress normal parts of the brain, causing severe nerve dysfunction. In many cases, benign brain tumors are also difficult to treat, like malignant tumors. Each year, over 190,000 people in the United States and 10,000 people in Canada are diagnosed with a primary or metastatic brain tumor. Brain tumors are the leading cause of solid cancer death in children under the age of 20. Although, brain tumors can be benign, the survival rate is lower than that of breast cancer. The incidence of metastatic brain tumors is estimated to be 10-15%, but it is growing with the increasing survival rate of tumor patients. At present, the prevalence rate in the United States is estimated to be 29.5 per 100,000, and glioma accounts for 50% of all brain tumors. Glial cells exist between the neurons and between the neuron and the blood vessel, and function to supply nutrients or oxygen to neurons. Many gliomas are malignant, and classified by the cell type or their features.
Gliomas are the most common type of primary brain tumor, and are associated with poor prognosis. High-grade astrocytomas including glioblastoma multiforme (GBM) and anaplastic astrocytoma (AA) are the most common intrinsic brain tumor m adults. While there has been progress in understanding the molecular genetics of high-grade astrocytomas, the cell type(s) of origin are still uncertain, and the molecular determinants of the disease's aggressiveness are not well understood. A better understanding of the cellular origin and molecular pathogenesis of these tumors may identify new targets for treatment of these neoplasms that are nearly uniformly fatal.
The grading of tumors is often critical to obtain an accurate diagnosis and prognosis of disease progression, and glioma is no exception. Decades of experience have led to a system of diagnosis of gliomas based on histology. Gliomas are histologically defined by whether they exhibit primarily astrocytic or oligodendroglial morphology. Gliomas are graded by cellularity, nuclear atypia, necrosis, mitotic figures, and micro-vascular proliferation, and all features associated with biologically aggressive behavior. This system of diagnosis has been developed over decades of clinical experience with gliomas and has now become the cornerstone of neuro-oncology [Kleihues, P. et al., World Health Organization (“WHO”) classification of tumors, Cancer 88: 2887 (2000)].
Satisfactory studies to develop an early, accurate and simple diagnosis of glioma with poor prognosis have not been conducted yet. Accordingly, the present inventors have made many efforts to develop an accurate diagnostic method for glioma. As a result, they found that locations of particular proteins and the number of protein-protein interactions differ between normal cells and glioma cells, which were visualized by FCCS (fluorescence cross-correlation spectroscopy), and glioma can be diagnosed by comparing the expression levels in the subcellular locations between normal cells and glioma cells through Western blotting, thereby completing the present invention.